You could buy either of the two dog newspapers, Dog World and Our Dogs (available in newsagents, but sometimes you have to order them, or you can subscribe) All sorts of shows are advertised there, with details of who to contact for schedules, or if you attend ringcraft, they often have schedules of local shows. Hope that helps.
Another for you to try is the the kennel club website http://www.the-kennel-club.org.uk/ Go to Shows on the left and then kennel gazette events diary Aug - Oct shows